Effect of Fe3O4‐doped sepiolite on the flammability and thermal degradation properties of epoxy composites

As‐received sepiolite/epoxy systems and Fe₃O₄‐doped sepiolite/epoxy systems were prepared, and the contents of sepiolite and Fe₃O₄‐doped sepiolite were kept as 2 and 4 wt%, respectively. Compared with sepiolite, the effect of Fe₃O₄‐doped sepiolite on the flame retardancy, combustion properties, thermal degradation, thermal degradation kinetics and thermomechanical properties of epoxy resin was investigated systematically by limiting oxygen index (LOI), cone calorimeter (Cone), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Some interesting results had been acquired. The addition of sepiolite decreased heat release rate, total smoke production and smoke production rate, and obviously improved LOI values of epoxy composites. Compared with sepiolite, the addition of Fe₃O₄‐doped sepiolite further reduced parameters mentioned above of epoxy composites, and further enhanced LOI values and char residues after cone test. There might be a synergistic effect between sepiolite and Fe₃O₄ on flame retardant epoxy composite. TGA results indicated that the addition of sepiolite had a slight effect on the thermal degradation of epoxy composites; however, the addition of Fe₃O₄‐doped sepiolite accelerated the thermal degradation of epoxy composites. DMA results showed that the addition of both sepiolite and Fe₃O₄‐doped sepiolite increased the glass transition temperature (T_g) of epoxy composite. The results obtained in this paper supplied an effective solution for developing excellent flame retardant properties of polymeric materials. Copyright © 2015 John Wiley & Sons, Ltd.     

磁性高强度聚丙烯酰胺/Fe3O4纳米复合水凝胶

以辐射过氧化的表面活性剂胶束为引发中心和交联中心, 制得具有优异机械性能的聚丙烯酰胺(PAAm)水凝胶, 并通过原位化学共沉淀法向其中引入Fe₃O₄粒子, 得到了磁性复合水凝胶. 扫描电子显微镜(SEM)表征发现磁性粒子在凝胶中分布均匀, 其粒径约为30 nm. X射线衍射(XRD)表征证实所引入的纳米粒子为尖晶石型Fe₃O₄. 磁性能测试表明, PAAm/ Fe₃O₄复合水凝胶具有超顺磁性特征. 该复合凝胶具有较优异的机械性能, 其断裂伸长率可以达到1200%, 拉伸强度最大可达0.10 MPa. 另外, 该复合凝胶表现出良好的形变回复特性.     

Fe_3O_4空心球/石墨烯复合吸波材料的制备及其性能

利用化学法制备氧化石墨烯(GO)与石墨烯(RGO),然后以水热法制备Fe3O4空心球/RGO复合吸波材料。XRD测试结果表明成功合成了具有立方结构的Fe3O4;SEM,TEM分析结果表明复合材料结构分布均匀,粒径约为100 nm。测试了材料在2~18 GHz波段的电磁参数,模拟计算了材料的反射率,结果显示复合材料的吸波性能比RGO有明显提升。当匹配厚度为7 mm时,复合材料具有两个吸收峰:在5.5 GHz处吸收峰为–9.5 d B,在16.5GHz处出现最大吸收峰–36 d B。     

Covalent bonding of magnetic Fe3O4 nanoparticles to aminopropyl‐functionalized magnesium phyllosilicate clay: Synthesis and cytotoxic potential investigation

Stable water dispersion of Fe₃O₄ magnetic nanoparticles (NPs) were successfully synthesized by using 3‐glycidoxypropyltrimethoxysilane (GPTMS) and Mg‐phyllo (organo) silicate known as aminoclay (AC) containing pendant amino groups with the approximate composition (R₈Si₈Mg₆O₁₆(OH)₄, R = CH₂CH₂CH₂NH₂). The Fe₃O₄‐GPTMS magnetic NPs with an epoxy functional group are suitable for forming a covalent bond with the amine group of aminoclay in an epoxy ring opening reaction. Appropriate Fe₃O₄‐GPTMS‐aminoclay (FG‐AC) magnetic composite are promising carriers for the targeting and delivery of platinum‐based anticancer drugs. Analysis of the cytotoxicity of the nanostructures on a K562 leukemia cell line using a colorimetery assay shows that both the FG‐AC and cis‐platin/FG‐AC magnetic composite were biocompatible. The nanostructures characterizations were investigated by Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy and energy dispersive analysis of X‐ray techniques. Magnetic measurement revealed that the saturated magnetization of the FG‐AC nanocomposite reached 7.6 emu/g and showed the characteristics of magnetism.     

Preparation and Characterization of Fe3O4/Ethiodized‐oil Magnetic Fluids Used in Arterial Embolization Hyperthermia

Fe₃O₄ nanoparticles (NPs) were prepared by the co‐precipitation of Fe³⁺ and Fe²⁺ with ammonium hydroxide, and were modified by four different surfactants. The modified Fe₃O₄ NPs were characterized by Fourier transform infrared spectroscopy, X‐ray powder diffraction, transmission electron microscopy and vibrating sample magnetometer. Then, the modified Fe₃O₄ NPs were dispersed in ethiodized‐oil by mechanical agitation and ultrasonic vibration to obtain stable Fe₃O₄/ethiodized‐oil magnetic fluids (MFs). The magnetic properties and rheological properties of the MFs were measured using a Gouy magnetic balance and a rotational rheometer, respectively. The saturation magnetization of the Fe₃O₄ modified by oleic acid was 52.1 emu/g. Furthermore, the result showed that the inductive heating effect of oleic acid stabilized Fe₃O₄/ethiodized‐oil MF was remarkable and it only took 650 s for the temperature rising from 25°C to 65°C. The specific absorption rate of the MF was 50.16 W/(g of Fe). It had a potential application in arterial embolization hyperthermia.     

Fe_3O_4/SrTiO_3复合光催化剂降解甲基橙

用共沉淀法制备了SrTiO3光催化剂及Fe3O4/SrTiO3复合光催化剂.通过紫外-可见漫反射光谱、XRD、SEM-EDX对其进行表征,以甲基橙为探针分子考察其光催化性能.结果表明,适量Fe3O4的掺入可明显提高Sr-TiO3光催化剂对可见光的吸收,从而增强其光催化性能;在光降解甲基橙的反应中,掺杂10%Fe3O4的SrTiO3光催化剂其催化活性是纯SrTiO3光催化剂的两倍.     

链霉亲和素-异硫氰酸荧光素偶联核壳型Fe3O4/Au纳米晶的合成及性质

采用改进的Polyol合成法,以PEO-PPO-PEO为表面活性剂制备了链霉亲和素-异硫氰酸荧光素偶联的Fe3O4/Au纳米粒子;利用透射电镜和X射线衍射仪分析证实了Fe3O4/Au的核壳型纳米结构,确定了其粒径和分布;采用紫外-可见吸收光谱仪和荧光光谱仪测定了所制备的纳米粒子的光学活性和荧光特性,并采用振动样品磁强计(VSM)测量了其磁化率.结果表明,所制备的Fe3O4/Au纳米粒子具有光学活性和荧光特性,以及优异的磁性.     

Fe_3O_4/RGO复合材料的制备及其电化学性能研究

以改进Hummers法合成的氧化石墨烯(GO)为前驱体,通过水热法结合烧结工艺制备了四氧化三铁/还原氧化石墨烯(Fe_3O_4/RGO)复合材料。利用X射线衍射(XRD)、拉曼光谱(Raman)、扫描电镜(SEM)、透射电镜(TEM)等手段对复合材料的理化性能进行表征;通过充放电测试、循环伏安(CV)和电化学阻抗谱(EIS)等技术,综合考察了材料的储锂性能及电化学性能增强机制。结果表明,在200和600 m A/g电流密度下,Fe_3O_4/RGO复合负极循环60次后的放电比容量分别保持在709和479 mAh/g,表现出良好的倍率性能;相较于纯Fe_3O_4负极,复合负极呈现出更优异的锂电性能,其电化学性能的改善得益于RGO能增强材料的电导性和结构稳定性。     

Simple Surfactant Concentration‐Dependent Shape Control of Polyhedral Fe3O4 Nanoparticles and Their Magnetic Properties

The shape and size of monodisperse Fe₃O₄ nanoparticles (NPs) are controlled using a chemical solution synthesis in the presence of the surfactant cetylpyridinium chloride (CPC). Cubic Fe₃O₄ NPs surrounded by six {100} planes are obtained in the absence of CPC. Increasing the CPC content during synthesis causes the shape of the resulting Fe₃O₄ NPs to change from cubic to truncated cubic, cuboctahedral, truncated octahedral, and finally octahedral. During this evolution, the predominantly exposed planes of the Fe₃O₄ NPs vary from {100} to {111}. The shape control results from the synergistic effect of the pyridinium cations, chloride anions, and long‐chain alkyl groups of CPC, which is confirmed by comparison with NPs synthesized in the presence of various related cationic surfactants. The size of the cubic Fe₃O₄ NPs can be tuned from 50 to 200 nm, by changing the concentration of oleic acid in the reaction solution. The Fe₃O₄ NPs exhibit shape‐dependent saturation magnetization, remanent magnetization, and coercivity.     

Fe3O4/聚苯乙烯纳米复合材料的结构与性能

采用油酸(OA)表面改性的粒径均一的Fe3O4纳米粒子(OA-Fe3O4)与工业化聚苯乙烯(PS)通过溶液共混挥发干燥方法得到了具有超顺磁性的OA-Fe3O4/PS纳米复合材料.透射电子显微镜表征结果表明,在OA-Fe3O4质量分数为1%~10%时,OA-Fe3O4纳米粒子均匀分散在PS聚合物基体中.示差扫描量热分析表明,随着纳米粒子加入量的增加,纳米复合材料的玻璃化转变温度逐渐降低.热失重分析表明,OA-Fe3O4的存在显著提高了PS在空气条件下的热稳定性.流变分析表明,随着纳米粒子加入量的增加(0~10%),复合材料黏度逐渐降低.进一步研究了分子量双峰分布的PS与OA-Fe3O4纳米复合体系的流变行为,结果表明,当PS基体的平均分子量大于临界缠结分子量,且填充的纳米粒子的半径小于双峰分布PS的均方旋转半径时,加入纳米粒子仍然导致体系的复合黏度降低.     

Waste to wealth: conversion of nano‐magnetic eggshell (Fe3O4@Eggshell) to Fe3O4@Ca(HSO4)2: cheap,green and environment‐friendly solid acid catalyst

Eggshell is a hazardous waste by European Union regulations, so that discarded thousands of tons per year. To convert waste (eggshell) to wealth (catalyst), nano‐magnetic eggshell was prepared based on the nano‐Fe₃O₄, and then the eggshell was converted to Ca(HSO₄)₂ with organic acid, namely, chlorosulfonic acid. Based on the back titration, 5.18 mmol SO₄H group was loaded per gram of the nano‐structure. Using this method eggshell was converted to cheap, green and environment‐friendly solid acid catalyst. The prepared catalyst (nano‐ Fe₃O₄@Ca(HSO₄)₂) was characterized by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), energy dispersive X‐ray spectroscopy (EDX), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and thermal gravimetric analysis (TGA). The activity of eggshell waste‐derived catalysts was successfully evaluated in the synthesis of value‐added products, namely indazolo[1,2‐b]‐phthalazinetrione derivatives as a benchmark multicomponent reaction. In addition, design of experiments shows that increase in amount of catalyst (and temperature), boost the reaction yield, especially with steeper slope at higher temperature.     

Synthesis,characterization and catalytic performance of core‐shell structure magnetic Fe3O4/P(GMA‐EGDMA)‐NH2/HPG‐COOH‐Pd catalyst

A strategy has been developed for the synthesis, characterization and catalysis of magnetic Fe₃O₄/P(GMA‐EGDMA)‐NH₂/HPG‐COOH‐Pd core‐shell structure supported catalyst. The P(GMA‐EGDMA) polymer layer was coated on the surface of hollow magnetic Fe₃O₄ microspheres through the effect of KH570. The core‐shell magnetic Fe₃O₄/P(GMA‐EGDMA) modified by ‐NH₂ could be grafted with HPG. Then, the hyperbranched glycidyl (HPG) with terminal ‐OH were modified by ‐COOH and adsorbed Pd nanoparticles. The hyperbranched polymer layer not only protected the Fe₃O₄ magnetic core from acid–base substrate corrosion, but also provided a number of functional groups as binding sites for Pd nanoparticles. The prepared catalyst was characterized by UV–vis, TEM, SEM, FTIR, TGA, ICP‐OES, BET, XRD, DLS and VSM. The catalytic tests showed that the magnetic Fe₃O₄/P(GMA‐EGDMA)‐NH₂/HPG‐COOH‐Pd catalyst had excellent catalytic performance and retained 86% catalytic efficiency after 8 consecutive cycles.     

Au/Fe3O4/壳聚糖纳米复合物NO2-传感电极

以壳聚糖为保护膜、玻碳为基底,用纳米Au和Fe₃O₄磁性纳米粒子构建了新型亚硝酸盐（NO₂^-）传感电极. 实验表明,该传感电极对NO₂^-有良好的电催化氧化活性,NO₂^-浓度(5.0×10^-6 ~ 2.0×10^-3 mol·L^-1)与氧化峰电流之间呈良好的线性关系（R = 0.9996）,检出限7.1×10^-7 mol·L^-1, 其灵敏度高、选择性好、重现性好.     

Fabrication and characterization of double‐shelled CeO2‐La2O3/Au/Fe3O4 hollow architecture as a recyclable and highly thermal stability nanocatalyst

A novel magnetic binary‐metal‐oxide‐coated nanocataly composing of a hollow Fe₃O₄ core and CeO₂‐La₂O₃ shells with Au nanoparticles encapsulated has been created in this work. The structural features of catalysts were characterized by several techniques, including SEM, TEM, UV‐vis, FTIR, XRD, XPS and TGA analyses. After the coating of CeO₂‐La₂O₃ layer, CeO₂‐La₂O₃/Au/C/Fe₃O₄ microspheres showed a superior thermal stability and catalytic reactivity compared with a pure CeO₂ or La₂O₃ layer. Accompanied by the burning of carbon layer, the specific surface could be increased by the formation of double‐shelled structure. Besides, the desired samples could be separated by magnet, implying the superior recycle performance. Using the reduction of 4‐nitrophenol by NaBH₄ as a model reaction, the microspheres exhibited highly reusability, superior catalytic activity, thermal stability, which are attributed to the unique double‐shelled structure of the support, uniform distribution of Au nanoparticles, the highly thermal stability of CeO₂‐La₂O₃ layer and mixed oxide synergistic effect. As a consequence, the unique nanocatalyst will open a promising way in the fabrication of the double‐shelled hollow binary‐metal‐oxide materials for future research and has great potential in other applications.     

l‐Proline‐functionalized Fe3O4 nanoparticles as a novel magnetic chiral catalyst for the direct asymmetric Mannich reaction

l ‐Proline has been successfully anchored on the surface of magnetic nanoparticles and characterized using powder X‐ray diffraction, scanning electron microscopy, vibrating sample magnetometry and Fourier transform infrared spectroscopy. These nanoparticles as a chiral catalyst have been employed to promote the direct asymmetric Mannich reaction. The corresponding products are obtained in high yields with high level of diastereoselectivity (up to 99:1 dr) in the presence of Fe₃O₄– l ‐proline. Also this heterogeneous catalyst can be recovered easily and reused many times without significant loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

正癸酸修饰磁性纳米Fe3O4对溶菌酶的吸附研究

以沉淀法制备了正癸酸修饰磁性纳米Fe3O4,采用XRD、TEM和FT-IR对修饰前后的磁性纳米粒子的形态、结构进行了表征。将修饰后的磁性纳米粒子用于对溶菌酶蛋白进行吸附分离,研究了溶液的pH、温度、时间、溶菌酶初始浓度、离子强度等因素对吸附过程的影响。结果表明:pH=10.7,吸附温度为25℃,吸附时间为2.0 h,溶菌酶初始浓度为0.30 mg·mL-1,最大吸附容量为35.0 mg·g-1。修饰后的磁性纳米粒子用于从鸡蛋清中提取溶菌酶,纯化倍数为30.9,酶活力收得率为73.0%。     

Disposable Amperometric Biosensor Based on Poly‐L‐lysine and Fe3O4 NPs‐chitosan Composite for the Detection of Tyramine in Cheese

An amperometric tyramine biosensor based on poly‐L‐lysine (PLL) and Fe₃O₄ nanoparticles (Fe₃O₄NP) modified screen printed carbon electrode (SPCE) was developed. PLL was formed on the SPCE by the electropolymerization of L‐lysine. Subsequently, Fe₃O₄NP suspension prepared in chitosan (CH) solution was casted onto the PLL/SPCE. Tyrosinase (Ty) enzyme was immobilized onto the modified Fe₃O₄?CH/PLL/SPCE and the electrode was coated with Nafion to fabricate the Ty/Fe₃O₄?CH/PLL/SPCE. Different techniques including scanning electron microscopy, chronoamperometry (i–t curve), cyclic voltammetry and electrochemical impedance spectroscopy were utilized to study the fabrication processes, electrochemical characteristics and performance parameters of the biosensor. The analytical performance of the tyramine biosensor was evaluated with respect to linear range, sensitivity, limit of detection, repeatability and reproducibility. The response of the biosensor to tyramine was linear between 4.9×10^?7–6.3×10^?5 M with a detection limit of 7.5×10^?8 M and sensitivity of 71.36 μA mM^?1 (595 μA mM^?1 cm^?2). The application of the developed biosensor for the determination of tyramine was successfully tested in cheese sample and mean analytical recovery of added tyramine in cheese extract was calculated as 101.2±2.1 %. The presented tyramine biosensor is a promising approach for tyramine analysis in real samples due to its high sensitivity, rapid response and easy fabrication.     

Fe_3O_4磁性纳米粒子催化动力学荧光法测定微量过氧化氢

Fe3O4磁性纳米粒子(Fe3O4MNPs)具有模拟过氧化氢酶的催化特性。基于Fe3O4MNPs催化H2O2氧化吡罗红建立了催化动力学荧光法测定H2O2的方法。对Fe3O4MNPs-吡罗红-H2O2体系的荧光光谱进行了研究,并考查了一些因素对体系的影响。所研究的催化反应分别在7~13min和13~18min内为假零级反应,对应的表观速率常数分别为1.33×10-1s-1和8.41×10-2s-1。反应时间为18 min时,催化反应的表观活化能为40.42 k J·mol-1。在最佳实验条件下,方法的线性范围为3.20×10-4~1.12×10-2mol·L-1,检出限为1.65×10-4mol·L-1。该法可用于消毒液、雨水、自来水及合成样品中H2O2含量的测定。     

Preparation for Magnetic Nanoparticles Fe3O4 and Fe3O4@SiO2 and Heterogeneous Fenton Catalytic Degradation of Methylene Blue

Dyestuff textile wastewater treatment has become a research hotspot due to its high chroma, poor biodegradability, and low toxicity characteristics. In this paper, we have synthesized magnetic Fe₃O₄ and core‐shell Fe₃O₄@SiO₂ materials by hydrothermal methods. These materials were characterized by XRD, TEM, N₂ adsorption‐desorption and so on. These materials’ heterogeneous Fenton has been applied to dye wastewater treatment. Methylene blue was used as a typical target of dye wastewater. Decolorization ratios of methylene blue were determined by different nanostructure composites catalysts. A serious of results of study showed that decolorization ratios of magnetic nanoparticles and core‐shell composites arrived at above 90 % under the weakly acidic or neutral conditions and room temperature. When these catalysts were reused, the results show that Fe₃O₄@SiO₂ materials were possessed with good cycle performance.     

Aptamer‐functionalized Fe3O4 magnetic nanoparticles as a solid‐phase extraction adsorbent for the selective extraction of berberine from Cortex phellodendri

The extraction adsorbent was fabricated by immobilizing the highly specific recognition and binding of aptamer onto the surface of Fe₃O₄ magnetic nanoparticles, which not only acted as recognition elements to recognize and capture the target molecule berberine from the extract of Cortex phellodendri , but also could favor the rapid separation and purification of the bound berberine by using an external magnet. The developed solid‐phase extraction method in this work was useful for the selective extraction and determination of berberine in Cortex phellodendri extracts. Various conditions such as the amount of aptamer‐functionalized Fe₃O₄ magnetic nanoparticles, extraction time, temperature, pH value, Mg²⁺ concentration, elution time and solvent were optimized for the solid‐phase extraction of berberine. Under optimal conditions, the purity of berberine extracted from Cortex phellodendri was as high as 98.7% compared with that of 4.85% in the extract, indicating that aptamer‐functionalized Fe₃O₄ magnetic nanoparticles‐based solid‐phase extraction method was very effective for berberine enrichment and separation from a complex herb extract. The applicability and reliability of the developed solid‐phase extraction method were demonstrated by separating berberine from nine different concentrations of one Cortex phellodendri extract. The relative recoveries of the spiked solutions of all the samples were between 95.4 and 111.3%, with relative standard deviations ranging between 0.57 and 1.85%.